21931940 has 24 divisors (see below), whose sum is σ = 46814712. Its totient is φ = 8628480.

The previous prime is 21931933. The next prime is 21931963. The reversal of 21931940 is 4913912.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 10816 + 21921124 = 104^2 + 4682^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7769 + ... + 10208.

It is an arithmetic number, because the mean of its divisors is an integer number (1950613).

Almost surely, 2^21931940 is an apocalyptic number.

21931940 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21931940 is an abundant number, since it is smaller than the sum of its proper divisors (24882772).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21931940 is a wasteful number, since it uses less digits than its factorization.

21931940 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18047 (or 18045 counting only the distinct ones).

The product of its (nonzero) digits is 1944, while the sum is 29.

The square root of 21931940 is about 4683.1549194960. The cubic root of 21931940 is about 279.9146848918.

The spelling of 21931940 in words is "twenty-one million, nine hundred thirty-one thousand, nine hundred forty".